Martin played center most of his Notre Dame career. But in 2014, Martin switched to guard while he dealt with torn thumb ligaments in his snapping hand and while he was still dealing with the lingering effects of ACL knee surgery he suffered in November 2013. His knee resulted in apparent limitations in 2014. Last year, he returned to center in 2015, but never regained preinjury mobility and agility, thus leaving him a better pass protector than a run blocker. This could reflect the athletic requirements of a zone blocking system. I've heard reasoning that he would take a full 2 years before a regaining the limits of his return. However, he was well past 2 years post surgery last season. His Combine was not all that impressive and he opted to skip participating in his Pro Day . Despite this, he was still ranked by many as the 2nd best center in the Draft. We'll have to see if in the stiffer competition presented in the NFL, he is able to overcome his limitations of movements and return to his 2013 agility level.